Combustor component with cooling holes formed by additive manufacturing

ABSTRACT

Combustor liners made using additive manufacturing techniques can employ cooling hole patterns which are not possible, or at least time consuming or expensive, to make using traditional subtractive manufacturing techniques. By additively manufacturing floatwall panels, cooling holes may be placed along axes that transect features on the floatwall panel, such as mounting studs, spacers, cooling pedestals, and rails.

STATEMENT OF GOVERNMENT INTEREST

This invention was made with U.S. Government support under Contract No. NNC10CA11C awarded by the National Aeronautics and Space Administration. The U.S. Government has certain rights in the invention.

BACKGROUND

The present invention relates to liners such as floatwall panels for use in gas turbine engine combustors, and in particular to floatwall panels with cooling holes for creating a cooling film. Combustors used in commercial gas turbine engines, such as those used in aircraft or power generation, may generate combustion gases at very high temperatures. These temperatures are often high enough to damage the combustor wall unless sufficient cooling is provided. The walls may be cooled in a variety of ways, including impingement cooling, transpiration cooling, effusion cooling, or convective cooling. The present invention relates to cooling holes used in effusion cooling.

For effective cooling by effusion in a gas turbine engine, many cooling holes are typically created through the wall of the combustion chamber. Often, the wall is made of many floatwall panels, each of which has cooling holes therein. The cooling holes may be made by laser ablation or electrical discharge machining. These methods of creating cooling holes have disadvantages. For example, electrical discharge machining is typically too slow and expensive to be a feasible option to manufacturers of combustor liners. Laser ablation is a faster, cheaper option, but suffers from line of sight limitations. That is, any other objects along the line of sight of the laser may be damaged by the laser during cooling hole machining. Various solutions have been proposed, such as placing wax or polytetrafluoroethylene behind the holes to prevent overshoot by the laser or angling cooling holes such that the laser does not include other features in its line of sight during machining. However, these solutions add to the cost and complexity of creating cooling holes with laser ablation. Designing a liner that avoids placing features along the line of sight of the laser limits potential cooling hole pattern options.

SUMMARY

According to the present invention, a floatwall panel has a cooling hole along an axis which transects a feature on the floatwall panel. The floatwall panel is made of several layers of sintered material.

Another embodiment of the invention is a method for making a floatwall panel using additive manufacturing. The method includes making a cooling hole along an axis which transects a feature on the floatwall panel.

Another embodiment of the invention is a gas turbine engine incorporating a floatwall panel made using additive manufacturing. The floatwall panel within the gas turbine engine has a cooling hole along an axis which transects a feature on the floatwall panel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a commercial combustor floatwall cross section.

FIG. 2 is a perspective view of a combustor floatwall panel with cooling holes.

FIG. 3 is a perspective view of a combustor floatwall panel, with cooling holes shown in phantom to illustrate their orientation.

FIG. 4 is a cross-sectional view of an additively manufactured combustor floatwall panel, showing individual layers of sintered material and a cooling hole arranged along an axis which transects a feature.

FIG. 5 is a perspective view of an additive manufacturing apparatus.

FIG. 6 is a cross-sectional view of the additive manufacturing apparatus of FIG. 5, taken along line 6-6.

DETAILED DESCRIPTION

FIG. 1 shows combustor 10, which includes fuel injector 12, shell 14, high pressure plenum 16, combustion chamber 18, fasteners 20, and floatwall panels 22. Downstream of combustor 10 is turbine section 24.

Fuel injector 12 is arranged on the upstream end of combustor 10. Airflow travels from fuel injector 12 through combustor 10, and exits combustor 10 into turbine section 24. Pressurized air passes through shell 14 from high pressure plenum 16 and into combustion chamber 18. Air is able to pass through shell 14 either through dilution holes (not shown) or cooling holes 30 (FIGS. 2, 3 and 4). Fasteners 20 attach floatwall panels 22 to shell 14.

Due to the intense heat generated by combustion, many combustors require cooling to protect the combustor from being damaged. One method used to cool the combustor is effusion cooling, in which cooling holes pass relatively cool air along the surface of the combustor near which combustion occurs. In effusion cooling, the air passed by these cooling holes preferably forms a cooling film, which prevents direct convective thermal transfer between the combustion gases and the combustor wall.

In the embodiment shown in FIG. 1, it is desirable to form an effusion film which does not include gaps where combustion gases come into contact with floatwall panels 22. Previously, placement and angle of cooling holes 30 (FIGS. 2 and 3) has been restricted by the placement of fasteners 20 and other features present on the surface of floatwall panels 22 which face high pressure plenum 16. Previously known methods of making floatwall panels 22 involve lasers or other subtractive manufacturing methods which can ablate or damage features located along the same axis as that defined by a cooling hole. Floatwall panels 22 as shown in FIG. 1 include cooling holes along axes which are transected by features on floatwall panels 22.

FIG. 2 shows floatwall panel 22 in perspective view, taken from the perspective of high pressure plenum 16 (FIG. 1). Floatwall panel 22 includes a plurality of cooling holes 30, as well as features built onto floatwall panel 22 including mounting studs 32, pedestals 34, and rail 36. Cooling holes 30 allow for effusion of air through floatwall panel 22 in order to create a cooling film protecting floatwall panel 22 from hot combustion gases. Mounting studs 32 facilitate attachment of floatwall panel 22 to other parts, such as shell 14 (FIG. 1). Pedestals 34 are used for various functions, such as impingement cooling or for spacing floatwall panel 22 from shell 14 (FIG. 1). Rail 36 likewise may be used for impingement cooling or spacing floatwall panel 22 from shell 14 (FIG. 1). Additionally, rail 36 may be used to maintain a desirable pressure differential between high pressure plenum 16 (FIG. 1) and combustion chamber 18 (FIG. 1). The features, including mounting studs 32, pedestals 34, and rail 36, may be formed of the same continuous piece of material as floatwall panel 22.

Floatwall panel 22 is designed to pass cooling air from one side to the other, to create a cooling air film. Floatwall panel 22 passes air from the outer side shown in FIG. 2 to the inner side. Cooling holes 30 are arranged along floatwall panel 22, and pass through floatwall panel 22 from the outer side facing shell 14 to the inner side facing combustion chamber 18 (FIG. 1). Notably, at least some cooling holes 30 are arranged along axes which are transected by features such as mounting studs 32, pedestals 34, or rail 36.

Cooling holes 30 as shown in FIG. 2 are arranged such that the axes defined by the cooling holes transect mounting studs 32, pedestals 34, and/or rail 36. The ability to place cooling holes in a broad range of angles and positions facilitates effusion cooling. If cooling holes 30 could only be positioned in locations where the axes defined by the cooling holes did not transect these features, the cooling film would have to be propagated by holes having different, limited angles or placements. Often, these different angles or placements are not ideal.

FIG. 3 shows the same floatwall panel 22 as shown in FIG. 2, with cooling holes 30 shown in phantom. FIG. 3 shows a portion of floatwall panel 22 with at least one of cooling holes 30 that is arranged along axis 38 which transects mounting stud 32.

FIG. 3 contains the same parts as shown in FIG. 2, including floatwall panel 22, cooling holes 30, and the mounting stud 32, pedestals 34, and rail 36 features. Cooling holes 30 are shown in phantom as they pass between opposite sides of floatwall panel 22. FIG. 3 shows axis 38 around which one cooling hole 30 is arranged which would not be possible to construct using previously known laser ablative technology without potentially damaging features such as mounting stud 32, pedestals 34, and/or rail 36.

In the section of cooling panel 22 shown in FIG. 3, one of the cooling holes 30 is arranged along axis 38, which transects mounting stud 32. Cooling holes 30 are arranged throughout cooling panel 22 at non-perpendicular angles from the surfaces of cooling panel 22. Thus, air may pass from the end shown closer to the viewer in FIG. 3 to the farther end through cooling holes 30, and at least one of the cooling holes 30 could not have been made using traditional laser ablation.

Laser ablation, which is used for the formation of many cooling hole patterns in other combustor liners, can damage any part which is along the line of sight defined by an axis through the center of the cooling hole. This limits the available placement of cooling holes to those placements which would not cause damage to mounting studs, pedestals, rails, or any other feature which extends from the floatwall panel. The panel shown in FIG. 3 may be designed with holes that are arranged along axes transecting features such as mounting stud 32, pedestals 34, or rail 36 without damaging those features.

FIG. 4 is a simplified cross-sectional view of a floatwall panel made using additive manufacturing methods. FIG. 4 includes floatwall panel 22, which is made up of a series of laminated layers of sintered material. FIG. 4 also shows the cross-section of mounting stud 32, and cooling hole 30. Cooling hole 30 is arranged along axis 38, which transects mounting stud 32.

The entire structure shown in FIG. 4 is made using additive manufacturing. Layers of sinterable material are applied to a substrate and selectively sintered. As additional layers are built, apertures are excluded from sintering that form a layerwise successively built hole. When sintering is complete, unsintered material may be removed while sintered material remains. This may be accomplished by blowing or brushing away excess material, often with an inert gas. Thus, by leaving unsintered apertures in each layer of material, cooling holes 30 may be formed. For some designs, additive manufacturing will leave a rough surface. This rough surface may be removed by, for example, machining or sanding the exterior of the finished part.

Unlike manufacturing by laser ablation, line of sight is not a factor in determining the pattern of cooling holes 30 in floatwall panel 22. For example, in the embodiment shown in FIG. 4, the line of sight along axis 38 transects mounting stud 32. Using traditional laser ablation manufacturing, the laser may have damaged mounting stud 32 while making cooling hole 30. Possible remedial measures, such as shielding mounting stud 32 with wax, may be expensive and/or time consuming. Other remedial measures may include using a reusable shielding material, such as a polytetrafluoroethylene sleeve, to protect stud 32 from laser overshoot. However, these sleeves must be specifically designed for the geometry of the component being shielded, and are only useful for a limited number of uses. It may be desirable to locate the entrance to cooling hole 30 very close to mounting stud 32, in which case shielding may not even be feasible.

FIG. 5 shows additive manufacturing apparatus 100. In particular, FIG. 5 shows an additive manufacturing apparatus which uses laser additive manufacturing to create a three-dimensional object out of sinterable, pulverant material. While direct metal laser sintering (DMLS) is described, other additive manufacturing techniques may be employed.

Additive manufacturing apparatus 100 includes a set of optical components, including laser 102, mirror 104, and moving optical head 106, which guide laser beam 108. Laser 102 may be any source of heating radiation, such as a CO2 laser. Additive manufacturing apparatus 100 also includes frame 110, pulverant material 112, and coater 114, which are used for powder containment and application. Pulverant material 112 may be any material suitable for use as a floatwall panel. Typically, pulverant material 112 will be some combination of ceramic and/or metal. For example, pulverant material 112 may be a high temperature superalloy. As shown in FIG. 5, partially built floatwall 22A contains hole segments 30A.

Laser 102 creates a laser beam which can be used for melting, sintering, or cutting. Laser 102 is pointed towards minor 104, which is arranged to deflect incident radiation toward moving optical head 106. In operation, laser 102 emits laser beam 108, which is deflected by mirror 104 and moving optical head 106 to selectively melt, sinter, or cut. Generally, laser beam 108 will be targeted within frame 110, which holds pulverant material 112. Coater 114 is arranged along a surface of frame 110, and may be moved across the surface of frame 110. Coater 114 may be, for example, a knife blade or a roller. As shown in FIG. 5, partially built floatwall 22A, including cooling hole segments 30A, is present inside frame 110.

In operation, laser beam 108 is generated by laser 102. Laser beam 108 is deflected by mirror 104 towards moving optical head 106. Moving optical head 106 directs laser beam 108 towards areas within frame 110 that include pulverant material 112 which are melted or sintered. Generally, the areas melted or sintered form a layer of a floatwall. In FIG. 5, partially built floatwall 22A is shown. Voids may be created within partially built floatwall 22A to form cooling hole segments 30A.

After each layer of partially built floatwall 22A is finished, the support holding partially built floatwall 22A (not shown) is lowered by the thickness of one layer of pulverant material 122, additional pulverant material 112 is added on top of the existing structures using coater 114, and the process is repeated. By repeating the process several times, a layer-by-layer object, such as a complete floatwall panel 22 (FIGS. 1, 2, 3 and 4), may be manufactured.

Traditional subtractive manufacturing utilizes laser ablation to remove the material where cooling holes are desired. This manufacturing method is problematic because other objects along the line of sight of the laser used in ablation may also be affected. Using the additive manufacturing method described above, various geometries may be created for cooling holes. Cooling holes may be created which are not straight, or which are arranged along axes which are transected by other features, including those proscribed by the line-of-sight limitations of laser ablation.

FIG. 6 shows additive manufacturing apparatus 100 of FIG. 5, taken along line 6-6. FIG. 6 is a cutaway view that shows the operation of additive manufacturing apparatus 100. FIG. 6 shows a DMLS apparatus, but it will be understood by those skilled in the art that other additive manufacturing techniques and apparatuses may be used.

Additive manufacturing apparatus 100 as shown in FIG. 6 includes many of the same parts as those shown in FIG. 5, such as frame 110, pulverant material 112, coater 114, and partially built floatwall 22A. FIG. 6 also shows component support 116 and material supply support 118. Component support 116 may be used to raise or lower partially built floatwall 22A. Material supply support 118 may be raised to elevate or lower pulverant material 112 above the working surface of frame 110.

FIG. 6 shows the arrangement of component support 116 and material supply support 118 in addition to the arrangement of parts shown in FIG. 5. As can be seen in FIG. 6, partially built floatwall 22A rests on component support 116 Likewise, pulverant material 112 rests on material supply support 118.

As each layer of partially built floatwall 22A is melted or sintered, component support 116 is lowered and material supply support 118 is raised. Coater 114 scrapes a layer of pulverant material 112 off of the top of the supply side and applies it in a layer across the top of partially built floatwall 22A. The process is then repeated until the floatwall panel is complete.

FIG. 6 shows one possible way of additively manufacturing a floatwall panel with cooling holes that are arranged along axes that are transected by features on the panel, such as mounting brackets, mounting studs, cooling pedestals, spacing pedestals, or rails.

While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention.

For example, in alternative embodiments, floatwall panels 22 may not be used, and a single shell liner may surround combustion chamber 18. The invention is applicable to the single shell type of liner as well, so long as the liner has features which create line-of-sight limitations for laser ablation of cooling holes.

Furthermore, while the embodiments disclosed herein refer to a single cooling hole arranged about an axis which transects a feature, the invention is not limited to a single hole. Rather, floatwall panels or combustor liners with one, two, or many holes along such axes are within the scope of this invention.

Alternative methods for additively manufacturing components are possible. For example, selective laser sintering, electron beam melting, laser powder deposition, or electron beam wire manufacturing may be used to create objects in an additive fashion.

In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Discussion of Possible Embodiments

The following are non-exclusive descriptions of possible embodiments of the present invention.

A combustor floatwall panel including a stack of layers of a sintered material, which form in the aggregate a panel having a first surface and a second surface parallel to the first surface, a feature disposed on the first surface, and a cooling hole that is made up of a series of apertures in adjacent layers, wherein the cooling hole extends between the first surface and the second surface, and is arranged along an axis that transects the feature.

The combustor floatwall panel of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:

the feature is one of a mounting bracket, a mounting stud, a cooling pedestal, or a rail;

the feature and the panel are made of a continuous piece of sintered material;

the combustor floatwall panel is made out of a sintered metal; and

the sintered metal is a high-temperature superalloy.

A method for making a combustor floatwall panel, including forming, by additive manufacturing, a multilayer structure including a wall, a feature protruding from the wall, and a series of interconnected apertures filled with a filler material; and removing the filler material from the interconnected apertures to create a cooling hole that extends through the wall and is aligned with an axis that transects the feature.

The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:

removing the filler material is accomplished using gas to blow away excess filler material;

machining the exterior of the combustor floatwall panel to achieve a smooth surface;

additively manufacturing includes selectively sintering a pulverant material;

selectively sintering the pulverant material comprises using laser additive manufacturing;

selectively sintering the pulverant material comprises using direct metal laser sintering;

selectively sintering the pulverant material comprises using an electron beam;

the feature is a mounting bracket, a mounting stud, a cooling pedestal, or a rail;

the filler material is a sinterable metal; and

the filler material is a high-temperature superalloy.

A gas turbine engine, including a compressor section, a turbine section, and a combustor section arranged between the compressor section and the turbine section, having a high pressure plenum in fluid communication with the compressor section, a combustion chamber in fluid communication with the turbine section; and at least one combustor floatwall panel made of layers of sintered material and arranged between the high pressure plenum and the combustion chamber, wherein the combustor floatwall panel is formed by additive manufacturing and includes a plurality of cooling holes at least one of which is aligned along an axis that transects a feature protruding from the panel.

The apparatus of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:

the feature is one of a mounting bracket, a mounting stud, a cooling pedestal, or a rail;

the feature and the combustor floatwall panel are made of a continuous piece of material;

the combustor floatwall panel is made of a sintered metal; and

the sintered metal is a high-temperature superalloy. 

1. A combustor floatwall panel comprising: a stack of layers of a sintered material, which form in the aggregate: a panel having a first surface and a second surface parallel to the first surface; a feature disposed on the first surface; and a cooling hole that is made up of a series of apertures in adjacent layers, wherein the cooling hole extends between the first surface and the second surface, and is arranged along an axis that transects the feature.
 2. The combustor floatwall panel of claim 1, wherein the feature is one of a mounting bracket, a mounting stud, a cooling pedestal, or a rail.
 3. The combustor floatwall panel of claim 1, wherein the feature and the panel are made of a continuous piece of sintered material.
 4. The combustor floatwall panel of claim 1, wherein the combustor floatwall panel is made out of a sintered metal.
 5. The combustor floatwall panel of claim 4, wherein the sintered metal is a high-temperature superalloy.
 6. A method for making a combustor floatwall panel, the method comprising: forming, by additive manufacturing, a multilayer structure including a wall, a feature protruding from the wall, and a series of interconnected apertures filled with a filler material; and removing the filler material from the interconnected apertures to create a cooling hole that extends through the wall and is aligned with an axis that transects the feature.
 7. The method of claim 6, wherein removing the filler material is accomplished using gas to blow away excess filler material.
 8. The method of claim 6, further comprising machining an exterior of the combustor floatwall panel to achieve a smooth surface.
 9. The method of claim 6, wherein additively manufacturing includes selectively sintering a pulverant material.
 10. The method of claim 9, wherein selectively sintering the pulverant material comprises using laser additive manufacturing.
 11. The method of claim 10, wherein selectively sintering the pulverant material comprises using direct metal laser sintering.
 12. The method of claim 9, wherein selectively sintering the pulverant material comprises using an electron beam.
 13. The method of claim 6, wherein the feature is a mounting bracket, a mounting stud, a cooling pedestal, or a rail.
 14. The method of claim 6, wherein the filler material is a sinterable metal.
 15. The method of claim 14, wherein the filler material is a high-temperature superalloy.
 16. A gas turbine engine comprising: a compressor section; a turbine section; and a combustor section arranged between the compressor section and the turbine section, the combustor section including a high pressure plenum in fluid communication with the compressor section; a combustion chamber in fluid communication with the turbine section; and at least one combustor floatwall panel made of layers of sintered material and arranged between the high pressure plenum and the combustion chamber, wherein the combustor floatwall panel is formed by additive manufacturing and includes a plurality of cooling holes at least one of which is aligned along an axis that transects a feature protruding from the panel.
 17. The gas turbine engine of claim 16, wherein the feature is one of a mounting bracket, a mounting stud, a cooling pedestal, or a rail.
 18. The gas turbine engine of claim 16, wherein the feature and the combustor floatwall panel are made of a continuous piece of material.
 19. The gas turbine engine of claim 18, wherein the combustor floatwall panel is made of a sintered metal.
 20. The gas turbine engine of claim 19, wherein the sintered metal is a high-temperature superalloy. 